atom/category.go

package atom

import (
	"encoding/xml"
	"errors"
	"fmt"
	"html"
)

type Category struct {
	XMLName xml.Name `xml:"category"`
	*CommonAttributes
	Term   string `xml:"term,attr"`
	Scheme string `xml:"scheme,attr,omitempty"` // IRI
	Label  string `xml:"label,attr,omitempty"`
}

// NewCategory creates a new Category. It returns a *Category and an error.
func NewCategory(term string) (*Category, error) {
	if term == "" {
		return nil, errors.New("error creating new category: term string empty")
	}

	return &Category{Term: term}, nil
}

// SetTerm sets the Term attribute of the Category. It returns an error.
func (c *Category) SetTerm(t string) error {
	if t == "" {
		return errors.New("error setting term of category: t string empty")
	}

	c.Term = t
	return nil
}

// SetScheme sets the Scheme attribute of the Category. It returns an error.
func (c *Category) SetScheme(s string) error {
	if !isValidIRI(s) {
		return fmt.Errorf("scheme %v not correctly formatted", s)
	}

	c.Scheme = s
	return nil
}

// SetLabel sets the Label attribute of the Category. It returns an error.
func (c *Category) SetLabel(label string) error {
	if label == "" {
		return errors.New("error setting label of category: label string empty")
	}

	c.Label = html.UnescapeString(label)
	return nil
}

// Check checks the Category for incompatibilities with RFC4287. It returns an
// error.
func (c *Category) Check() error {
	if c.Term == "" {
		return fmt.Errorf("term attribute of category %v empty", c)
	}

	if c.Scheme != "" {
		if !isValidIRI(c.Scheme) {
			return fmt.Errorf("scheme attribute of category %v not correctly formatted", c)
		}
	}

	if !isCorrectlyEscaped(c.Label) {
		return fmt.Errorf("label attribute of category %v not correctly escaped", c)
	}

	return nil
}